Flux jumps and mechanical effects in high-temperature superconductors with multi-field coupling model

Abstract

Mechanical deformation during the magnetization process of high-temperature superconductors can lead to the deterioration in their critical current. A multi-field coupling model involving four physical fields is established to investigate the role of mechanical strain in the flux jump of the superconducting bulk. The electrical, magnetic, thermal, and mechanical coupling behavior is presented and analyzed under different applied fields. The simulation results of the coupled model are compared with experimental data, which showing an agreement. The numerical results indicate that in the superconductors, mechanical deformation significantly affects the electrical, magnetic, and thermal properties owing to a reduction in the critical current density under mechanical strain. The moment and location of magnetic flux jump will change as the mechanical strain is considered. Interestingly, the occurrence of magnetic flux jumps during field-cooling magnetization leads to a decrease in stress in bulk superconductor, suggesting that the fracture may not be caused by flux jumps, which is contrary to common understanding. Moreover, the temperature changes uniformly at different locations within the superconducting bulk. In the extended study, the thermo-magnetic and mechanical properties of the bulk material under ZFCM are presented using the coupled model. The effect of mechanics on the flux jump differs between FCM and ZFCM, which is attributed to the nonlinear changes in the electric field.